1. Field of the Disclosure
The present disclosure relates to a capacitive type humidity sensor with a humidity-sensitive polymer film as dielectrics and a manufacturing method thereof.
2. Description of the Related Art
Humidity sensors, which uses a measurement of humidity change, include an electrostatic capacitive type humidity sensor with a humidity-sensitive polymer film, where a permitivity changes in accordance with the amount of moisture which is absorbed or released, as dielectrics. The capacitive type humidity sensor is provided with the humidity-sensitive polymer film and a sensor section formed of a pair of electrodes which are covered with the humidity-sensitive polymer film and which detect electrostatic capacitance, and it is possible for pads which are provided at an edge portion of the pair of electrodes to be electrically connected to an external circuit using wire bonding. A capacitive type humidity sensor such as this is, for example, disclosed in Japanese Unexamined Patent Application Publication No. 2008-107166.
In the structure in the related art described above, there is a problem in that the humidity-sensitive polymer film and the bonding wire become exposed and the bonding wire is susceptible to impact and corrosion. In particular, in a structure where a control IC which is an external circuit is provided on the same support substrate as the sensor section, there is a desire to seal the entire substrate so as to protect the control IC and the wire bonding section from damage due to impact and corrosion, but it is necessary that the humidity-sensitive polymer film of the sensor section is exposed to air and it is not possible to perform a sufficient seal.
In addition, among the capacitive type humidity sensors, there is a type where a sensor section where the electrostatic capacitance changes in accordance with humidity and a reference section which maintains a constant electrostatic capacitance irrespective of humidity are provided on the same substrate and the difference in capacitance between the sensor section and the reference section is converted into a voltage and output the voltage. In this type, there is a concern that, if the substrate surface is exposed and the humidity-sensitive polymer film of the sensor portion is exposed to air, it may not be possible to obtain sufficient sealing of the reference portion.